A conventional bicycle hub is used for positioning the wheel axle so that the wheel is rotatable about the axle, and generally includes the hub, the axle, the rotatable unit and the ratchet disk. A driving unit and derailleur mechanism are cooperated with the hub when needed. The conventional hubs are cataloged by one-way driving and two-way driving, wherein the one-way driving means that the hub can only rotate in the specific direction which usually the forward direct of the bicycle, and the two-way driving hub means that the hub can be rotated in both directions.
The one-way driving hub uses ratchet teeth to drive the wheel in one direction and the ratchet teeth do not output mechanical work when driving in the other direction so that when the pedals are not treaded, the bicycle wheel still rotate for keep the bicycle moving forward. The engagement of the ratchet teeth of one-way driving bicycle hub can be engaged in radial direction or in axial direction. The radial-direction ratchet teeth extend radially from the hub and are engaged with the pawls in radial direction and the axial-direction ratchet teeth extend axially from the hub and are engaged with the pawls in axial direction.
Taiwan Utility Model Patent No. 099200755 discloses a bicycle hub and comprises a hub mounted to an axle and a recess is defined in one end of the hub. The recess includes multiple ratchet recesses defined therein. A ratchet member is rotatably mounted to the axle and includes a disk which has multiple notches. The disk is engaged with the recess and the notches are alternatively arranged into two groups, and any two adjacent notches are separated by one pitch. Each notch has a pawl which is biased by a spring.
Taiwan Utility Model Patent No. 096219287 discloses a bicycle hub and comprises a magnetic collar which has multiple teeth located around the center thereof and the teeth extend axially. A ring-shaped magnetic pawl which has two end faces, the outer end face is engaged with the teeth and movable in axial direction. A circular ratchet member is connected to the other end face of the ring-shaped magnetic pawl and is connected to a free wheel. The circular ratchet member is engaged with the ring-shaped magnetic pawl in one direction. More than on permanent magnet is connected to the ring-shaped magnetic pawl where no circular ratchet member is connected.
The Taiwan Utility Model Patent No. 099200755 discloses that any two adjacent notches are separated by one pitch and each notch has a pawl which is biased by a spring. When the cyclist pedals forward, the system chooses the pawl that is located close to the notch as the pushing pawl. Taiwan Utility Model Patent No. 096219287 discloses a circular ratchet member connected to the end face of the ring-shaped magnetic pawl and is engaged with the free wheel in one direction. The ring-shaped magnetic pawl and the circular ratchet member are made by magnetic material so that they are always located in the collar by the permanent magnet and in contact with the end surface of the free wheel to operate under small resistance.
The present invention intends to provide a ratchet mechanism for a bicycle hub and improves the drawbacks of the prior arts mentioned above, wherein the pawl and the ring-shaped member have larger contact surface which accelerates the wearing therebetween and the significant friction also slows the movement of the pawl which cannot quickly return to its original position.